I can sit you can sit she can sit we can sit you can sit they can sit
V-ing form
I can be sitting you can be sitting she can be sitting we can be sitting you can be sitting they can be sitting
Perfect
I can have sat you can have sat she can have sat we can have sat you can have sat they can have sat
V-ing perfect
I can have been sitting you can have been sitting she can have been sitting we can have been sitting you can have been sitting they can have been sitting
Negation
Simple form
I cannot sit you cannot sit she cannot sit we cannot sit you cannot sit they cannot sit
V-ing form
I cannot be sitting you cannot be sitting she cannot be sitting we cannot be sitting you cannot be sitting they cannot be sitting
Perfect
I cannot have sat you cannot have sat she cannot have sat we cannot have sat you cannot have sat they cannot have sat
V-ing perfect
I cannot have been sitting you cannot have been sitting she cannot have been sitting we cannot have been sitting you cannot have been sitting they cannot have been sitting
Interrogative form
Simple form
can I sit? can you sit? can she sit? can we sit? can you sit? can they sit?
V-ing form
can I be sitting? can you be sitting? can she be sitting? can we be sitting? can you be sitting? can they be sitting?
Perfect
can I have sat? can you have sat? can she have sat? can we have sat? can you have sat? can they have sat?
V-ing perfect
can I have been sitting? can you have been sitting? can she have been sitting? can we have been sitting? can you have been sitting? can they have been sitting?
Interro-negative form
Simple form
can I not sit? can you not sit? can she not sit? can we not sit? can you not sit? can they not sit?
V-ing form
can I not be sitting? can you not be sitting? can she not be sitting? can we not be sitting? can you not be sitting? can they not be sitting?
Perfect
can I not have sat? can you not have sat? can she not have sat? can we not have sat? can you not have sat? can they not have sat?
V-ing perfect
can I not have been sitting? can you not have been sitting? can she not have been sitting? can we not have been sitting? can you not have been sitting? can they not have been sitting?